Neuroendocrine tumors and secretion: towards the development of new diagnostic and therapeutic tools – SecretoNET

Neuroendocrine tumors (NET) is a heterogeneous group of neoplasms arising from hormone/peptide-secreting cells from the gastrointestinal and bronchopulmonary systems, breast, skin, and central nervous system. Today NET currently lack adequate diagnostic tests and targeted therapies either than surgery, which result in higher morbidity and mortality.
Although NET are heterogeneous, a critical feature they all share are dysfunctional secretory pathways mainly leading to hypersecretion which is known to induce severe clinical complications and to favor NET development. While hypersecretion by NETs is well known to pathologists and clinicians, it has never been explored at the cellular and molecular level in human tumor cells. We hypothesized that understanding how secretion is regulated in NET will considerably inform novel drug development strategies and help in more accurate diagnostic test developments. Thus, the objectives of this project are i) to establish what cellular mechanisms are responsible for specific secretion dysfunction in NET in order to characterize new potential target candidates and thus preventing hypersecretory activity of the NETs; ii) to characterize new biomarkers able to diagnose NETs more accurately. To achieve these ambitious goals, we have developed a close cooperation between industrial developers specialized in biomarker-based diagnostics (Firalis), cell biologists from academic research specialized in neuroendocrine secretion (INCI, CNRS) and a world leader company in mass spectrometry-based proteomics services (Caprion).

To investigate which step(s) of the secretory process is/are disturbed, we will apply carbon fiber amperometry on primary culture of both human pheochromocytoma and gastro-intestinal carcinoid, two NETs that arise from (entero)chromaffin cells of the adrenal medulla and the gastro-intestinal tract and which are characterized by an excess of catecholamine and serotonin secretion, respectively. Amperometry is a technique that enables precise measurement of individual exocytotic event dynamics in real time.
Our preliminary data also comprehensively characterized and partially validated potential biomarker and target candidates from pheochromocytoma. In the present proposal, we will pursue biomarker validation and expand to clinical evaluation by testing serum samples from additional types of NET, as well as healthy controls and confounding diseases using a targeted multiple reaction monitoring mass spectrometry (MRM-MS) assay. In parallel we will raise and evaluate antibodies directed against the biomarker candidates best suited for an immunoassay approach, which is routinely used in laboratories. The performance of the candidate biomarkers will be then confirmed with an independent set of clinical and control serum samples which will be tested using predefined combinations of biomarkers. We expect here to identify biomarkers with the necessary performance for clinical diagnostic applications, as well as assays to use them with.

Finally, the combination of amperometric recording of tumor cell secretion with the detection of exocytotic protein expression changes by MS will allow us to identify specific steps of the exocytotic process that are dysregulated in the tumor as well as new key components of the molecular machinery triggering hypersecretion. Functional analyses on the role in tumor secretion of few identified candidates will allow us to propose key protein candidates that could be potentially targeted to inhibit tumor-associated-hypersecretion.

In conclusion, our proposal has ambitious goals, far beyond the scope of a single laboratory and requires the cooperation outlined here. Taking into account our solid preliminary data, the expertise of our consortium, the cooperation between academic research and private companies and the innovative methodology applied, we do believe that we are able to create the unique synergy needed to succeed.